Activists are now calling on District Attorney George Gascón to immediately file criminal charges against the officer.
Police officials said the altercation happened following a traffic stop Sunday. It's unclear what led to the traffic stop.
In a post on X, LAPD said the officer involved has been removed from field duties.
Bystander video posted on social media shows two officers arresting an unidentified man. The man is handcuffed with his hands behind his back and asks, "What did I do, though?" An officer then throws a punch and hits the man in the jaw.
Civil rights activist Najee Ali held a news conference Monday outside the LAPD's Southeast Station and called on Gascón to press charges against the officer.
"It's horrific. This officer does not need a badge or a gun," Ali said. "He needs handcuffs and a jail cell for what he did. He should be arrested and prosecuted."
Ali is in touch with the man's friends and family. He said the man is humiliated by the viral clip.
Civil rights leaders are planning to attend a Police Commission meeting Tuesday to address the incident.